terminal: Clean trycheckout status when picking up a new module

If two consecutive modules were to fail with trycheckout enabled,
jhbuild would get quite confused as the last tried recovery phase didn't
get reset properly.

This would cause jhbuild to go straight to eg. the force_checkout phase
if the previous module built by forcing the configure phase, or bail out
completely if the previous module failed.

https://bugzilla.gnome.org/show_bug.cgi?id=723082